© 2019 IOP Publishing Ltd. Silver nanoparticles were synthesized in aqueous solution using an ecofriendly, fast, and easy photochemical technique through the use of Albizia lebbeck (L) Benth seed (ALS) extract and sunlight. The phytochemical screening of ALS extract revealed the presence of reducing carbohydrates, and saponins. Also, infrared spectroscopy analysis of the ALS extract confirms the presence of functional groups, characteristics of these compounds. The experiments were conducted near noon during winter by exposing aqueous mixtures of silver nitrate and ALS extract to sunlight at 25 °C. The nanoparticles were characterized by optical absorption spectroscopy, Fourier-transform infrared spectroscopy, and scanning transmission electron microscopy. The nanoparticle formation was evaluated by following the temporal evolution of the absorbance. This data was analyzed using first-order kinetics, finding good correlation to the experimental data. The nanoparticle micrograph analysis shows narrow size distribution and acceptable polydispersity indices. The sunlight driven synthesis of silver nanoparticles using ALS extract is more effective to produce small spheroidal AgNPs than sodium citrate. In addition, ALS extract inhibits the growth of nanoparticles with different morphologies, even when both reducing agents are incorporated at the same time. The proposed methodology presents a reliable and sustainable way to obtain small-sized silver nanoparticles according to the principles of green chemistry.